Bacterial β-carbon-sulfur lyase (β-CSL)

Bacterial β-carbon-sulfur lyase (β-CSL) enzymes represent a family of microbial enzymes responsible for cleaving β-carbon–sulfur bonds in sulfur-containing amino acids and their conjugates, such as L-cysteine and L-methionine, to generate volatile sulfur compounds (VSCs) including hydrogen sulfide, methyl mercaptan, and dimethyl sulfide[1][4][5]. Major gene-encoded forms include methionine γ-lyase (mdeA), cystathionine γ-lyase, and homocysteine desulfhydrase (mccB)[1][2][4]. These enzymes play a central role in oral malodor (halitosis), are key virulence factors for periodontopathogenic bacteria (e.g., Fusobacterium nucleatum, Porphyromonas gingivalis, Treponema denticola), and can modulate the composition and function of the oral microbiota[5][6]. Production of VSCs by these enzymes is directly linked to the breakdown of proteinaceous substrates and is regulated by factors like the presence of pyridoxal phosphate as a cofactor[1]. Enzyme activity and gene expression can be potential therapeutic targets or diagnostic biomarkers for oral and extra-oral diseases associated with the microbiome[4][5][6].

Other names

Bacterial β-C-S lyaseBacterial volatile sulfur compound–producing enzymeMicrobial β-C-S lyaseMethionine γ-lyase (for specific VSCs from methionine)Cystathionine γ-lyaseCystathionine β-synthaseHomocysteine desulfhydrasemdeA (methionine γ-lyase gene)mccB (homocysteine desulfhydrase gene)

Enzyme inhibition leading to decreased VSC production and reduction of halitosis Targeting oral microbiome composition to suppress VSC-producing bacteria Potential use of PLP (pyridoxal phosphate) antagonists to block enzyme cofactors